Last updated: February 24, 2025
Experience September weather in Portland, where the landscape undergoes a beautiful transition. With maximum temperatures reaching up to 35°C (95°F) and an average of 18°C (64°F), warmth persists alongside the refreshing coolness of the season, with minimums dipping to 6°C (42°F). While the city enjoys pleasant conditions, it also faces 62 mm (2.4 in) of precipitation spread over 8 days, infusing the air with a refreshing humidity level of 71%. This combination creates a unique tapestry of vibrant atmospheres, inviting both locals and visitors to enjoy the dynamic charm of Portland in September.
In September, Portland experiences a delightful transition as summer begins to fade. The temperatures range from a comfortable 6°C (42°F) at night to an average daytime high of 18°C (64°F), peaking at a warm 35°C (95°F) on the hottest days. This month marks a subtle shift from the sweltering heat of August, where highs reached a scorching 40°C (104°F), to a more temperate climate perfect for outdoor activities. The crisp fall air begins to replace the summer warmth, setting the stage for the vibrant colors of autumn while still allowing for those pleasant, sunny afternoons that make September a favorite among locals and visitors alike.
In September, Portland experiences a noticeable shift as summer wanes and the rainy season begins to re-emerge. With 62 mm (2.4 inches) of precipitation falling over 8 days, this month marks a moderate uptick in moisture compared to the drier summer months of July and August, which recorded only 6 mm (0.2 in) and 8 mm (0.3 in), respectively. As autumn approaches, the drop in temperature invites increased rainfall, setting the stage for the wetter months ahead. This trend underscores September's transitional nature, balancing the tail end of summer's dryness with the promise of fall's refreshment, making it a vivid time in the city's climate calendar.
As summer transitions to autumn, September in Portland marks a noticeable shift in humidity levels. After the warm and drier months of July and August, where humidity dipped to 82% and 74% respectively, September brings a further decline to 71%. This is the lowest point of the year, creating a refreshing atmosphere that contrasts sharply with the high humidity levels seen in the winter months, peaking at 87% in November and December. Such fluctuating humidity trends throughout the year contribute to Portland's reputation for its vibrant and varied climate, making September an ideal time to enjoy the outdoors before the rainy season sets in.
As summer gives way to fall, September in Portland sees a notable shift in sun intensity, with the UV Index registering at 7—indicating a high exposure category. This marks a gradual decline from the peak of 10 in July and June, where the risk of harm from unprotected sun exposure was at its highest. With a burn time of 25 minutes, it's essential to stay vigilant as the sun can still be quite powerful, especially during midday. September serves as a gentle reminder to enjoy the tail end of outdoor activities while being mindful of sun protection. For more details, check out Portland UV Index.
UV Risk Categories
As summer gracefully transitions into autumn, September in Portland boasts a wealth of sunshine, contributing 268 hours of golden rays to the city. This month, while slightly less sun-drenched than the peak of July with its impressive 374 hours, still shines brighter than the dreary winter months like January with only 88 hours. September’s warmth is a comforting reminder of the sunny days that came before it, as daylight gently begins to dwindle compared to the vibrant August. The gradual decline in daylight hours heralds the advent of fall, but for now, Portlanders can savor the lingering sunshine before the crispness of October settles in. This harmonious blend of warmth and change makes September a delightful month to experience the beauty of the Pacific Northwest.
In Portland, September marks a transitional phase in the weather, where the chances of sunny days hold a promising 50%. This is a significant uptick compared to the earlier months, particularly from the cloudy days of winter, which dropped to as low as 16% in January and November. As summer reaches its end, the city enjoys a gradual decline in sunshine probability, notably from the 74% in July, before tapering off in the fall. While September retains a balanced chance for sunny skies, it is part of a general trend of increasing sunlight from the gloom of winter to the vibrant days of summer. This makes early September an excellent time for outdoor activities, as the pleasant weather and mild temperatures create an inviting backdrop for exploring the city’s beauty.
As September arrives in Portland, the city transitions into a new rhythm, marked by a slight decrease in daylight. With 12 hours of light, this month signals the beginning of autumn, following the peak of long days in June and July, which boasted 15 hours of daylight. The gradual reduction from summer's brightness reflects the shifting seasons, as the impressive 14 hours in May and 13 hours in August give way to shorter days, beckoning cooler weather and vibrant fall leaves. This natural ebb and flow in daylight not only enhances the beauty of the Portland landscape but also invites residents to savor outdoor activities before the days shorten further into 10 hours by October.
As September ushers in the transition from summer to fall in Portland, the average wind speed settles at a gentle 2.3 m/s (5 mph). This slight dip from the preceding summer months illustrates a consistent pattern—Portland experiences relatively calm winds throughout most of the year, particularly from June to August. Moving into the autumn months, wind speeds begin to pick up, peaking in October at 2.7 m/s (6 mph), suggesting a gradual increase in breezy days as the season progresses. This creates a pleasant atmosphere for residents and visitors alike, setting the stage for Portland's enchanting fall scenery marked by colorful foliage dancing in the breeze. Overall, September's mild winds reflect the city's serene environment, making it a perfect time for enjoying outdoor adventures.
The weather in Portland changes throughout the year, offering a unique experience in each season. Below is a month-by-month comparison of September's weather with other months, highlighting differences in temperature, precipitation, and other key factors. Click on each section to discover seasonal trends in Portland and find detailed weather information for every month.
In September, the weather is considerably warmer, with average temperatures reaching up to 18°C (64°F) and maximums soaring to 35°C (95°F). The month sees moderate precipitation across eight days, totaling 62 mm (2.4 in), alongside a relative humidity of 71%. In contrast, January presents a starkly different climate, characterized by colder temperatures, where the average hovers around 5°C (42°F) and lows can plummet to -14°C (7°F). January experiences significantly higher precipitation, with 163 mm (6.4 in) spread over 17 days, and a higher humidity level at 85%. For those interested in a detailed breakdown of conditions during this chilly month, check out Portland weather in January.
Comparing the weather in September and February reveals a stark contrast in temperatures and precipitation patterns. September enjoys milder temperatures, with a minimum of 6°C (42°F) and an average of 18°C (64°F), reaching highs of 35°C (95°F). In contrast, February experiences colder conditions, with temperatures dipping as low as -7°C (19°F) and averaging only 5°C (41°F). Additionally, February is notably wetter, receiving 172 mm (6.8 in) of precipitation over 19 days, compared to September's 62 mm (2.4 in) spread across 8 days. The humidity also rises in February to 84%, compared to September's 71%. For more detailed insights into the weather patterns, you can check Portland weather in February.
September and March exhibit distinctly different weather patterns. In September, temperatures range from a minimum of 6°C (42°F) to a maximum of 35°C (95°F), with an average of 18°C (64°F), making it a warmer month overall. In contrast, March experiences cooler temperatures, with a low of -4°C (26°F) and a high of 24°C (75°F), averaging just 8°C (46°F). Additionally, March sees significantly more precipitation, with 135 mm (5.3 in) over 17 days compared to September's 62 mm (2.4 in) across 8 days. The humidity also rises in March to 85%, higher than September's 71%. For a more detailed look at March weather, you can visit Portland weather in March.
When comparing the weather in September and April, significant differences emerge. September boasts higher average temperatures, ranging from a minimum of 6°C (42°F) to a maximum of 35°C (95°F), making it feel much warmer overall, with an average of 18°C (64°F). In contrast, April experiences cooler temperatures, with a typical range from -1°C (31°F) to 29°C (84°F) and an average of 11°C (51°F). Additionally, April tends to be wetter, receiving more precipitation at 117 mm (4.6 in) over 15 days, compared to September's 62 mm (2.4 in) across just 8 days. The humidity is also slightly higher in April at 83%, compared to September's 71%. For a closer look at Portland's weather during this month, you can visit Portland weather in April.
September weather generally features warmer temperatures compared to May, with an average temperature of 18°C (64°F) and a maximum reaching up to 35°C (95°F). In contrast, May sees lower averages, with a maximum of 32°C (90°F) and an average of 14°C (58°F). Although both months have similar precipitation levels, September experiences slightly more rain (62 mm vs. 58 mm) but over fewer days (8 days vs. 10 days in May). Additionally, humidity is higher in May at 83%, compared to 71% in September. For more detailed information, you can check Portland weather in May.
When comparing the weather in September and June, we see some notable differences. September tends to have a slightly wider range in maximum temperatures, reaching up to 35°C (95°F), compared to June's striking maximum of 47°C (118°F). Both months have similar average temperatures of around 18°C (64°F), but June experiences higher humidity at 83%, which can make the warmth feel more intense than in September, where humidity is at 71%. Additionally, while September has more precipitation at 62 mm (2.4 in), both months see rainfall roughly on 8 days. For more detailed insights into the specifics of June's weather, you can visit Portland weather in June.
In comparing the weather of September and July, September displays a wider temperature range, with minimums dipping to 6°C (42°F) and maximums soaring to 35°C (95°F). Although the average temperature is slightly lower in September at 18°C (64°F) compared to July's average of 21°C (69°F), it experiences more variability. Precipitation in September is higher, at 62 mm (2.4 in) over 8 days, contrasting sharply with July's minimal rainfall of just 6 mm (0.2 in) over only 1 day. Additionally, September's humidity stands at 71%, while July is more humid at 82%. For more details on July’s weather, you can check out Portland weather in July.
In comparing the weather between August and September, we see a notable shift in temperature and precipitation patterns. August boasts higher temperatures, with a minimum of 9°C (48°F) and an average of 21°C (70°F), peaking at a scorching 40°C (104°F). In contrast, September experiences cooler temperatures, ranging from a minimum of 6°C (42°F) to an average of 18°C (64°F), and reaching a maximum of 35°C (95°F). Additionally, September sees increased rainfall, with 62 mm (2.4 in) of precipitation spread over 8 days, compared to August's relatively dry conditions, which had only 8 mm (0.3 in) over 2 days. Humidity levels also shift slightly, with September at 71% and August at 74%. For more detailed information, you can check Portland weather in August.
September weather features a warm average temperature of 18°C (64°F), with daytime highs reaching up to 35°C (95°F), making it a month of lingering summer warmth. However, it experiences relatively low precipitation, totaling 62 mm (2.4 in) across about 8 days, and maintains a humidity level of 71%. In contrast, October ushers in autumn with a noticeable drop in temperatures, where the average is around 12°C (53°F), with a minimum of -2°C (29°F) and a maximum of 26°C (79°F). This month also brings increased rainfall, with 105 mm (4.1 in) spread over 12 days and a higher humidity level of 81%. For more details, check out Portland weather in October.
September and November present stark contrasts in weather patterns. In September, temperatures can range from a mild 6°C (42°F) at night to a warm maximum of 35°C (95°F) during the day, with an average of 18°C (64°F). The month also sees relatively low precipitation, totaling 62 mm (2.4 in) over about 8 days, along with a humidity level of 71%. In contrast, November experiences much cooler temperatures, with minimums plummeting to -5°C (24°F) and an average of just 8°C (47°F), while maximums reach 19°C (67°F). This month is significantly wetter, accumulating 155 mm (6.1 in) of rainfall across 18 days, and has a higher humidity of 87%. For more detailed information, check out Portland weather in November.
September and December present contrasting weather patterns. In September, temperatures range from a minimum of 6°C (42°F) to a maximum of 35°C (95°F), with an average of 18°C (64°F). The month enjoys relatively moderate precipitation of 62 mm (2.4 in) over 8 days and a humidity level of 71%. In contrast, December sees a significant drop in temperatures, with a minimum of -5°C (24°F), an average of 5°C (41°F), and a maximum of 16°C (60°F). Precipitation increases substantially to 183 mm (7.2 in) over 19 days, accompanied by higher humidity at 87%. For more detailed insights about December weather, check out this link: Portland weather in December.
As summer transitions into fall, September in Portland showcases a delightful blend of warm days and cooler evenings, creating a unique climate profile that stands out from other months. With an average temperature that balances between the sweltering heat of late summer and the crispness of early autumn, residents enjoy pleasant outdoor conditions, despite the occasional rain, with about eight days of precipitation. The increased humidity adds a touch of summer's lingering warmth, making for a typically vibrant and enjoyable month. To delve deeper into Portland's weather trends, explore more at Portland Climate.